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Thioarsenates in geothermal waters of yellowstone National Park: Determination, preservation, and geochemical importance

Environmental Science and Technology

By:
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DOI: 10.1021/es070273v

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Abstract

Mono-, di-, tri-, and tetrathioarsenate, as well as methylated arsenic oxy- and thioanions, were determined besides arsenite and arsenate in geothermal waters of Yellowstone National Park using anion-exchange chromatography inductively coupled plasma mass spectrometry. Retention time match with synthetic standards, measured S:As ratios, and molecular electrospray mass spectra support the identification. Acidification was unsuitable for arsenic species preservation in sulfidic waters, with HCl addition causing loss of total dissolved arsenic, presumably by precipitation of arsenic-sulfides. Flash-freezing is preferred for the preservation of arsenic species for several weeks. After thawing, samples must be analyzed immediately. Thioarsenates occurred over a pH range of 2.1 to 9.3 in the geothermal waters. They clearly predominated under alkaline conditions (up to 83% of total arsenic), but monothioarsenate also was detected in acidic waters (up to 34%). Kinetic studies along a drainage channel showed the importance of thioarsenates for the fate of arsenic discharged from the sulfidic hot spring. The observed arsenic speciation changes suggest three separate reactions: the transformation of trithioarsenate to arsenite (major initial reaction), the stepwise ligand exchange from tri- via di- and monothioarsenate to arsenate (minor reaction), and the oxidation of arsenite to arsenate, which only becomes quantitatively important after thioarsenates have disappeared. ?? 2007 American Chemical Society.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Thioarsenates in geothermal waters of yellowstone National Park: Determination, preservation, and geochemical importance
Series title:
Environmental Science and Technology
DOI:
10.1021/es070273v
Volume
41
Issue:
15
Year Published:
2007
Language:
English
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Environmental Science and Technology
First page:
5245
Last page:
5251